<% content_for :sub_menu  do %>
  <% cache :controller=>"article_categories",:action=>"list" do %>
  <% ArticleCategory.find(:all,:conditions=>"parent_id is not null").each do |item| -%>
    <%=link_to item.name,list_article_category_articles_path(item) %>
  <% end -%>
  <% end %>
<% end -%>